1. Field of the Invention
The present invention relates to a pillar garnish which is joined to a front pillar portion of an automobile, and more particularly to a structure for joining a pillar garnish including an air bag.
2. Description of the Related Art
Hitherto, passengers of an automobile are safely protected from a shock caused from collision by an air bag apparatus provided for the front portion and side portions in the cabin. To prevent collision of the head of a passenger with a side glass or the like in the event of a shock exerted from the side surface of an automobile, a pillar garnish 60 including an air bag A on the reverse side thereof is, in recent years, joined to a pillar portion 75 of the front portion of the car body, as shown in FIG. 19. The pillar garnish 60 including the air bag is structured such that an inflater I disposed adjacent to an instrument panel P generates gas with which the air bag A is expanded as shown in FIG. 20. Thus, the air bag A is expanded, thereby causing the pillar garnish 60 to be pushed and bent toward the inside portion of a cabin. Thus, a gap for permitting the air bag A to expand is formed between the pillar portion 75 of the car body and the pillar garnish 60. The air bag A passes through the gap so that the air bag A is developed between a head T of a passenger and a window glass G as indicated with a chain line Bo shown in FIG. 19. As a result, the head T of a passenger can be prevented.
The pillar garnish 60 including the air bag is structured such that great pressure is applied to the pillar garnish 60 in a direction toward the inside portion of the cabin when the air bag A is expanded and developed. Therefore, the pillar garnish 60 must be joined in such a manner that separation of the pillar garnish 60 from the pillar portion 75 of the car body and undesirable flying of the same can be prevented.
Hitherto, a joining structure, with which undesirable debris of the pillar garnish can be prevented, has been known which is arranged such that a bolt insertion hole in the form of a through hole is formed in each of upper and lower intermediate portions of the pillar garnish. Moreover, a bolt inserted into each bolt insertion hole is clamped and secured to the pillar portion of the car body. Note that the lower end of the pillar garnish is inserted into a hole or the like formed in the instrument panel P so as to be secured.
The joining structure using the bolt is arranged such that the pillar garnish is, in the bolt securing portion, completely secured to the pillar portion of the car body. Therefore, excessively large stress is exerted on the bolt securing portion when expansion of the air bag causes the side portion of the pillar garnish to be pressed and bent. Hence it follows that a conventional pillar garnish made of ABS resin (Acrylonitrile-Butadiene-Styrene resin) or PPF (PolyPropylene with inorganic material, for example, talc) cannot endure the foregoing stress. Thus, there is apprehension that the foregoing pillar garnish is broken. What is worse, the foregoing joining structure using the bolt must be arranged such that the operation for clamping the bolt can be performed from the designed surface (from the cabin portion) of the pillar garnish. Therefore, the head of the bolt appears on the designed side of the pillar garnish, causing the appearance to deteriorate. Accordingly, a blind cover is fitted to the bolt insertion hole from the designed surface of the pillar garnish. The blind cover portion is, however, easily recognized, causing the appearance to deteriorate.
To solve the above-mentioned problem caused from the blind cover, a structure, as shown in FIG. 21, may be employed in which a seat portion 62 is integrally formed to project over the reverse side of a predetermined position of a pillar garnish 60. Moreover, a head 66 of a rod-shape fixing metal member 65, such as a bolt, is embedded in the seat portion 62. Another end 69 of the rod-shape fixing metal member 65 is inserted and secured to the inside portion of an engaging hole 76 formed in an inner panel 71 of a pillar portion 75 of the car body. The rod-shape fixing metal member 65 is made of metal and incorporating a shaft portion 67 which has an end formed into a head 66 having a large diameter. Another end 69 of the shaft portion 67 is provided with an engaging portion 68. The illustrated rod-shape fixing metal member 65 incorporates a bolt and a nut which is the engaging portion 68. Referring to the drawing, symbol F represents a front glass, symbol C represents an electric line extended from an engine room, reference numeral 77 represents an opening trim, 78 represents a glass-run channel and 79 represents a body frame.
When the joining structure shown in FIG. 21 is employed, the existence of a side surface 63 of the seat portion 62 causes the thickness of the pillar garnish 60 to locally be changed. Hence it follows that sink mark 64 easily occurs, as shown in FIG. 22. As a method of preventing occurrence of the sink mark 64, a method may be employed with which thickness K2 of the side surface 63 of the seat portion 62 is made to be smaller than thickness K1 of the outer portion of the seat portion (it is preferable that K2 is 1/2 of K1). If the thickness K2 of the side surface 63 of the seat portion 62 is reduced until the sink mark 64 can be prevented, concentration of stress causes a crack to be formed in a base portion 61a of the side surface 63 of the seat portion 62 which serves as a hinge portion when the pillar garnish 60 is pushed and bent owing to the expansion of the air bag A, as shown in FIG. 23.
The pillar garnish 60 structured as described above is formed such that the head 66 of the rod-shape fixing metal member 65 comprising the bolt or the like is directly insert-molded. In the foregoing case, the following fact is known: embedding of the head 66 causes the thickness of the resin portion of the pillar garnish upper than the head 66, that is, the thickness of the resin portion of the pillar garnish which is surrounded by the side surface 63 of the seat portion 62 to be nonuniform. In this case, the foregoing structure easily encounters sink mark occurring in the designed surface of the pillar garnish 60. The foregoing portion of a usual pillar garnish which is secured by the bolt or the like is usually formed into a curved surface owing to a requirement for improving the design quality. The head 66 of the usual rod-shape fixing metal member 65, such as the bolt, is formed into a flat shape. Therefore, the distance from the surface of the head 66 of the rod-shape fixing metal member 65 to the designed surface of the pillar garnish 60, that is, the thickness of the resin portion of the pillar garnish in the foregoing portion cannot easily be uniformed. Thus, occurrence of the sink mark cannot be prevented. When the thickness of the resin portion of the pillar garnish which is surrounded by the side surface 63 of the seat portion is attempted to be constant, the surface of the head 66 of the rod-shape fixing metal member 65 is formed to have a shape corresponding to the designed surface of the pillar garnish 60. To employ the foregoing structure, a specially-designed rod-shape fixing metal member is required. In the foregoing case, required cost reduction is not permitted.
Moreover, it is preferable that the foregoing joining structure is arranged in such a manner that the quantity of projection of the pillar garnish 60 into the cabin is reduced to enlarge the space in the cabin in usual state. Moreover, when the air bag A is expanded, smooth expansion of the air bag A must be permitted by maximally enlarging the space for accommodating the air bag A, that is, maximally elongating the distance from the pillar portion 75 of the car body to the pillar garnish 60. Therefore, the foregoing joining structure is arranged such that when the pillar garnish 60 has been pressed against the inside portion of the cabin owing to the expansion of the air bag A, movement of the rod-shape fixing metal member 65 together with the pillar garnish 60 in a direction toward the cabin for a predetermined distance must be permitted. To achieve this, the side surface of a shaft portion 67 of the rod-shape fixing metal member 65 is not engaged to the engaging hole 76. As an alternative to this, a state is realized in which the side surface is simply inserted into the engaging hole 76. Moreover, clearance M required to permit sliding of the rod-shape fixing metal member 65 is provided between the engaging hole 76 and the engaging portion 68 of the another end 69 of the shaft portion 67. In addition, another clearance N for facilitating the operation exists between the outer surface of the shaft portion 67 of the rod-shape fixing metal member 65 and the inner surface of the engaging hole 76. Since the clearances M and N exist as described above, looseness is sometimes felt in a usual state when the pillar garnish 60 is, from the inside portion of the cabin, pressed at a position adjacent to the head portion 66 of the rod-shape fixing metal member 65. When the automobile is being driven, there is apprehension that vibrations cause the shaft portion 67 of the rod-shape fixing metal member 65 to be brought into contact with the engaging hole 76 and noise to be produced.